• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.242-247
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• 1998

In this study, we have synthesized $ZnGa_2O_4$:Mn,X powder doped with Mn, MnO, $MnF_2$ and $MnCl_2$, low voltage green emitting phosphor, in vacuum atmosphere. From PL spectra, the intensity of the emission peak, the brightness with coactivator show that $ZnGa_2O_4$:Mn,Cl > $ZnGa_2O_4$:Mn,F > $ZnGa_2O_4$:Mn,O > $ZnGa_2O_4$:Mn. These improvement of the brightness are caused by the increase of the concentration of $Mn^{2+}$ ion. In case of $ZnGa_2O_4$:Mn,Cl and ZnGa$_2$O$_4$:Mn,F, the brightness is enhanced much more, which is owed to the decrease of defect of host material. For $ZnGa_2O_4$:Mn,Cl phosphor fabricated with optimized condition, the decay time becomes short from 30 ms of the $ZnGa_2O_4$:Mn and $ZnGa_2O_4$:Mn,O to 6 ms and the brightness of CL at 1 kV, 1 mA is 60 cd/$m^2$.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.479-486
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• 2009

In natural environments, manganese (Mn) exists in the valence of +2, +3, and +4 and plays a pivotal role as a strong oxidant or reductant in the geochemical cycles of elements. Especially, Mn forms varying (oxyhydr)oxides. The oxidation state of structural Mn is characteristic to each oxide and is one of the most important factors controlling its geochemical behaviors such as solubility, sorption capacity, and redox potential. Therefore, it is important to elucidate processes governing Mn oxidation state in predicting the fate and transport of many redox sensitive elements in the environment. X-ray photoelectron spectroscopy (XPS) is a very useful method to determine the oxidation state of various elements in solid phases. In this study, the oxidation states of structural Mn in MnO, $Mn_2O_3$, $MnO_2$ were assessed based on the binding energy spectra of $Mn2p_{3/2}$ and Mn3s using XPS and were compared with those reported elsewhere. $Mn2p_{3/2}$ binding energies were determined as 640.9, 641.5, 641.8 eV for MnO, $Mn_2O_3$, $MnO_2$, respectively, which indicates that the binding energy increased with increasing Mn oxidation state. It was also noted that Ar etching may cause changes in electronic structure configuration on surface of the original sample.

• Economic and Environmental Geology
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• v.53 no.6
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• pp.687-694
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• 2020

Two oxidizing agents (KMnO4, H2O2), and one neutralizing agent (NaOH) were applied to evaluate Mn removal in mine drainage. A Mn2+ solution and artificial mine drainage were prepared to identify the Fe2+ influence on Mn2+ removal. The initial concentrations of Mn2+ and Fe2+ were 0.1 mM and 1.0 mM, respectively. The injection amount of oxidizing and neutralizing agents were set to ratios of 0.1, 0.67, 1.0, and 2.0 with respect to the Mn2+ mole concentration. KMnO4 exhibited a higher removal efficiency of Mn2+ than did H2O2 and NaOH, where approximately 90% of Mn2+ was removed by KMnO4. A black MnO2 was precipitated that indicated the oxidation of Mn2+ to Mn4+ after an oxidizing agent was added. In addition, MnO2 (pyrolusite) is a stable precipitate under pH-Eh conditions in the solution. However, relatively low removal ratios (6%) of Mn2+ were observed in the artificial mine drainage that included 1.0 mM of Fe2+. The rapid oxidation tendency of Fe2+ as compared to that of Mn2+ was determined to be the main reason for the low removal ratios of Mn2+. The oxidation of Fe2+ showed a decrease of Fe concentration in solution after injection of the oxidizing and neutralizing agents. In addition, Mn7+ of KMnO4 was reduced to Mn2+ by Fe2+ oxidation. Thus, the concentrations of Mn increased in artificial mine drainage. These results revealed that the oxidation method is more effective than the neutralization method for Mn removal in solution. It should also be mentioned that to achieve the Mn removal in mine drainage, Fe2+ removal must be conducted prior to Mn2+ oxidation.

• Korean Journal of Environmental Agriculture
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• v.29 no.1
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• pp.77-85
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• 2010

Reactive oxygen species (ROS) are very harmful to living organisms due to the potential oxidation of membrane lipids, DNA, proteins, and carbohydrates. transformed E.coli strain QC 871, superoxide dismutase (SOD) double-mutant, with three sequence variant MnSOD1, MnSOD2, and MnSOD3 manganese superoxide dismutase (MnSOD) gene isolated from wheat. Although all QC 871 transformants grown at $37^{\circ}C$ expressed mRNA of MnSOD variants, only MnSOD2 transformant had functional SOD activity. MnSOD3 expressed active protein when grown at $22^{\circ}C$, however, MnSOD1 did not express functional protein at any growing and induction conditions. The sequence comparison of the wheat MnSOD variants revealed that the only amino acid difference between the sequence MnSOD2 and sequences MnSOD1 and 3 is phenylalanine/serine at position 58 amino acid. We made MnSOD2S58F gene, which was made by altering the phenylalaine to serine at position 58 in MnSOD2. The expressed MnSOD2S58F protein had functional SOD activity, even at higher levels than the original MnSOD2 at all observed temperatures. These data suggest that amino acid variation can result in highly active forms of MnSOD and the MnSOD2S58F gene can be an ideal target used for transforming crops to increase tolerance to environmental stresses.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.583-590
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• 1997

The effects of Mn2O3 and Y2O3 additives on the microstructure and dielectric properties of Sr(Zr, Ti)O3 have been investigated. Powders with Sr(Zr1-xTix)O3(0$\leq$x$\leq$0.1) composition were prepared by the conventional solid state processing from commercial TiO2 and precipitation-processed ZrO2. The powders containing sintering additives of Mn2O3 and Y2O3 were compacted and then sintered at 1,55$0^{\circ}C$ for 4 h to get>97% relative density. Mn2O3 suppressed the grain growth and Y2O3 enhanced the density of sintered body. The oxidation state of Mn ions were determined by a chemical wet method and EPR spectroscopy. Mn ions were present as Mn2+ and Mn4+ in SrZrO3, while as Mn3+ and Mn4+ in Ti-substituted Sr(Zr, Ti)O3. With the substitution of Ti, the lattice parameters of SrZrO3 decreased and its dielectric constant increased with remarkable decrease in Q value. The dielectric constant of Sr(Zr, Ti)O3 was in the range of 30 to 40, Q values 1,200~5,400 at 6 GHz and temperature coefficient of resonant frequency -67~100 ppm/K.

• Korean Journal of Materials Research
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• v.6 no.1
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• pp.90-98
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• 1996

Mn((Cu0.66AI0.34)1-x(Bi0.3Sb0.7)x) 및 Mn((Fe0.66AI0.34)1-x(Bi0.3Sb0.7)x) 합금계의 상의 변화와 자기적 특성을 조사하였다. Mn((Cu, SI)(Bi, Sb)) 합금계는 Bi상, MnSb상, MnBi상, k-상, Heuser상, Mn2Sb 및 $\beta$-Mn상의 혼합상으로 이루어졌으며 x가 증가함에 따라 Bi상과 Mn2Sb상이 증가하고 K-상, Heusler상 및 $\beta$-Mn상이 줄어들거나 사라졌다. 자기적 성질은 자성을 띄는 MnSb상, MnBi상, Mn2Sb상, k-상 및 Hseusler상과 비자성인 Bi상과 $\beta$-Mn상의 상대적 분율에 의해 결정됨을 알 수 있었고, 150K-200K 부근에서 그 이하로 온도가 감소함에 따라 자화값이 급격히 감소하는 현상이 나타났다. Mn((Fe, AI)(Bi, Sb))합금계는 Bi상, MnSb상, MnBi상, MnBi상,$\beta$-Mn상, k-상 및 Mn2Sb상의 혼합상으로 나타났으며, 자기적 성질은 조사한 전 조성에서 강자성을 띄고 있음을 알 수 있었다.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.541-547
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• 2011

Nanorod-clustered $MnO_2$ precursors with ${\alpha}$-, ${\beta}$-, and ${\gamma}$-phases are synthesized by hydrothermal reaction of $MnSO_45H_2O$ and $(NH_4)S_2O_8$. The formation of nanorod-clustered ${\beta}-MnO_2$ is particularly confirmed under the conditions of high reactant concentration and hydrothermal reaction at $150^{\circ}C$. The spinel $LiMn_2O_4$ nanorod-clusters are also prepared by lithiating the $MnO_2$ precursors, varying the concentration of lithiating agent ($LiC_3H_3O_2{\cdot}2H_2O$) and heat treatment temperature, and characterized for use as cathode material of lithium-ion batteries. As a result, the nanorod-clustered $LiMn_2O_4$ prepared from the ${\beta}-MnO_2$ at higher $LiC_3H_3O_2{\cdot}2H_2O$ concentration and the annealing at $800^{\circ}C$ is proven to show the cubic spinel structure and to achieve the high initial discharge capacity of 120 mAh/g.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.131-137
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• 2011

A simple and rapid electrochemical method for the quantitative analysis of $Mn^{2+}$ ion is demonstrated with a view to examine the $Mn^{2+}$ dissolution behavior of $LiMn_2O_4$. The method described herein is based on the oxidation reaction of $Mn^{2+}$ to $Mn^{4+}(MnO_2)$ in aqueous buffer solution. Under the optimum condition (pH 8.9 0.04 M $NH_3-NH_4Cl$ buffer solution and glassy carbon working electrode), the linear range of $5{\mu}M-100{\mu}M$ (0.275-5.5 ppm) [$Mn^{2+}$] is obtained for the Linear sweep voltammetry(LSV) and $0.2{\mu}M-10{\mu}M$ (0.011-0.55 ppm) [$Mn^{2+}$] for the differential pulse voltammetry (DPV), respectively. It is also noted that the oxidation reaction of $Mn^{2+}$ ion is reduced with increasing amount of the electrolyte ($LiPF_6$, EC, EMC) added to the measuring solution, which is found to be mainly due to $LiPF_6$ and EC rather than EMC.

• Journal of the Korean Ceramic Society
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• v.44 no.11
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• pp.639-644
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• 2007

Spinel pigments, developing black color in high temperature glazes at oxidation or reduction atmosphere, without CoO because of its high price were synthesized by solid solution method. Ten mixed compositions consisted of NiO, MnO, $Fe_2O_3 and $Mn_2O_3$ were fired at $1250^{\circ}C$ for 1h. The resulting pigments were characterized by using XRD, FT-IR, SEM and UV-vis spectrometer. Structure of the pigments are spinel and particles' shape are spherical or cubic. Glazed tiles containing 5 wt% pigments were fired at $1260^{\circ}C$ and $1240^{\circ}C$ in reduction atmosphere. Color in glazes were analyzed by UV-vis spectrometer. Colors of NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.4875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0125 mole% and NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.3875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.1125 mole% in lime glaze showed black in oxidation, in reduction NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.4875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0125 mole% and NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.55{\cdot}Mn_2O_3$ 0.0125 mole% showed black. In case of lime-barium glaze, NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.3875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.1125 mole%, NiO 0.975 MnO $0.075{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% and NiO 0.925 MnO $0.075{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% showed black color in oxidation and NiO 0.875 MnO $0.125{\cdot}Fe_2O_3$ $0.3875{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.1125 mole%, NiO 0.925 MnO $0.075{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% and NiO 0.725 MnO $0.275{\cdot}Fe_2O_3$ $0.4375{\cdot}Cr_2O_3$ $0.50{\cdot}Mn_2O_3$ 0.0625 mole% showed black one in reduction.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.50-54
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• 1999

We have measured the x-ray photoemission spectroscopy of cation deficient La0.970Mn0.970O3 as a function of temperature. Detailed results on the chemical shifts and changes in Mn 2p and Lp 3d core levels due to variation of temperature have been obtained. The Mn 2p 3/2 and 1/2 main peaks and La 3d core spectrum shift to lower binding energy levels with increasing temperature. This XPS behavior is correlated with the strength of localization of Mn3+. The Jahn-Teller effect due to Mn3+ besides the conventional random potential effects is likely to localize charge carriers in La-.970Mn0.970O3.